test: enable addons test to pass with debug build

Currently when running configure with the --debug option in combination
with the tests (./configure --debug && make -j8 test) there are a few
addon tests that fail with error messages similar to this:

=== release test ===
Path: addons/load-long-path/test
fs.js:558
  return binding.open(pathModule._makeLong(path), stringToFlags(flags),
mode);
                 ^

Error: ENOENT: no such file or directory, open
'/nodejs/node/test/addons/load-long-path/build/Release/binding.node'
    at Object.fs.openSync (fs.js:558:18)
    at Object.fs.readFileSync (fs.js:468:33)
    at Object.<anonymous>
(/nodejs/node/test/addons/load-long-path/test.js:28:19)
    at Module._compile (module.js:560:32)
    at Object.Module._extensions..js (module.js:569:10)
    at Module.load (module.js:477:32)
    at tryModuleLoad (module.js:436:12)
    at Function.Module._load (module.js:428:3)
    at Module.runMain (module.js:594:10)
    at run (bootstrap_node.js:382:7)
Command: out/Release/node
/nodejs/node/test/addons/load-long-path/test.js

This commit allows for the tests to pass even if the configured build
type is of type debug.

PR-URL: https://github.com/nodejs/node/pull/8836


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>